A certain conventional hydrogen-fueled internal combustion engine supplies hydrocarbon fuel and hydrogen gas to a combustion chamber for combustion purposes while a regular internal combustion engine uses gasoline or other hydrocarbon fuel for combustion purposes. This type of hydrogen-fueled internal combustion engine uses hydrogen gas as fuel in addition to hydrocarbon fuel and improves the combustion efficiency by making use of the fast burn and other characteristics of the hydrogen gas. Since the combustion efficiency improves, the air-fuel ratio can be shifted toward a leaner region (that is, the lean limit can be raised). As a result, it is possible to lower the fuel consumption rate and reduce the amounts of NOx (nitrogen oxide) exhaust, THC (total hydrocarbon) exhaust, and the like. This type of hydrogen-fueled internal combustion engine is disclosed, for instance, by the following Patent Documents.
Patent Document 1: Japanese Patent Laid-Open No. 2004-116398
Patent Document 2: Japanese Patent Laid-Open No. 2004-239138
Patent Document 3: Japanese Patent Laid-Open No. 2003-293809
Patent Document 4: Japanese Patent Laid-Open No. 2004-100501